1. Preheat oven to 350F. If slices of roast beef are large, cut in half.
2. Split rolls, if needed, and brush olive oil on the inside of each roll.
3. Place bread, cut side down, on a baking sheet and place in oven. Toast for 5-8 minutes, until lightly golden brown.
4. Remove from oven, but keep rolls on baking sheet. Set aside. Don’t turn off oven.
5. While rolls are toasting, add remaining olive oil to a skillet over medium heat.
6. Add beef broth, coconut aminos, garlic powder, onion powder, and Worcestershire sauce.
7. Whisk together. Turn heat up a bit and bring to a simmer. Simmer for 5 minutes to allow flavors to meld.
8. After 5 minutes, add balsamic vinegar and stir. Taste and season with additional salt, if desired.
9. Drop in roast beef and, using tongs, toss for about 1 minute. You don’t want the roast beef to cook, just warm.
10. Divide roast beef (draining excess liquid back into the pan) equally between sandwich rolls.
11. If desired, place sandwiches in oven for a couple minutes to get hot. This is an optional step as they will be served with hot au jus.
12. Place each sandwich on a plate and serve with a small bowl of au jus for dipping.